As an example of a vehicle brake system that applies a braking force to a vehicle, a brake system for a hybrid vehicle disclosed in, for example, the patent document 1 is known. According to the vehicle brake system disclosed in the patent document 1, an input piston and a master piston are retained while being spaced apart from each other by a predetermined distance. A required friction braking force is calculated by removing a regenerative braking force from a required braking force which is calculated on the basis of a detected amount of movement of the input piston. A servo pressure generated by a pressure accumulating portion (an accumulator) and a linear valve is applied to the master piston on the basis of the required friction braking force, thereby the master piston is moved and a master pressure is generated. The master pressure is applied to a wheel cylinder, and the friction braking force is generated by the master pressure.
Patent Document 1: JP2012-16984A